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PubMed1992

The respiratory system as an exercise limiting factor in normal trained subjects.

Recently, we have shown that an untrained respiratory system does limit the endurance of submaximal exercise (64% peak oxygen consumption) in normal sedentary subjects. These subjects were able to increase breathing endurance by almost 300% and cycle endurance by 50% after isolated respiratory training. The aim of the present study was to find out if normal, endurance trained subjects would also benefit from respiratory training. Breathing and cycle endurance as well as maximal oxygen consumption (VO2max) and anaerobic threshold were measured in eight subjects. Subsequently, the subjects trained their respiratory muscles for 4 weeks by breathing 85-160 l.min-1 for 30 min daily. Otherwise they continued their habitual endurance training. After respiratory training, the performance tests made at the beginning of the study were repeated. Respiratory training increased breathing endurance from 6.1 (SD 1.8) min to about 40 min. Cycle endurance at the anaerobic threshold [77 (SD 6) %VO2max] was improved from 22.8 (SD 8.3) min to 31.5 (SD 12.6) min while VO2max and the anaerobic threshold remained essentially the same. Therefore, the endurance of respiratory muscles can be improved remarkably even in trained subjects. Respiratory muscle fatigue induced hyperventilation which limited cycle performance at the anaerobic threshold. After respiratory training, minute ventilation for a given exercise intensity was reduced and cycle performance at the anaerobic threshold was prolonged. These results would indicate the respiratory system to be an exercise limiting factor in normal, endurance trained subjects.

Adolescent↗

PubMed2002

Relationship of exercise test variables to cycling performance in an Ironman triathlon.

The purpose of this study was, firstly, to investigate the intensity of exercise performance of highly trained ultra-endurance triathletes during the cycling portion of an Ironman triathlon, and, secondly, to examine the anaerobic threshold and its relationship to this performance. Following a peak oxygen consumption (VO(2peak)) test on a cycle ergometer to determine the heart rate (HR(Th,vent)) and power output (PO(Th,vent)) at the ventilatory threshold (Th(vent)), 11 highly trained male triathletes [mean (SEM) age 35.8 (1.6) years, body fat 11.7 (1.2)%. VO(2peak) 67.5 (1.0) ml x kg(-1) x min(-1)] who were participating in an Ironman triathlon, in random order: (1) cycled at their PO(Th,vent) (Bi(Th,vent)) until they were exhausted, and (2) cycled for 5 h at a self-selected intensity (Bi(SSI)). Cycling power output (PO), oxygen uptake (VO(2)), heart rate (HR) and blood lactate concentration ([La(-)](b)) were recorded at regular intervals during these trials, while performance HR was recorded during the cycling phase of the Ironman triathlon. Significantly greater (P < 0.05) values were attained during Bi(Th,vent) than during Bi(SSI) for PO [274 (9) compared to 188 (9) W], VO(2) [3.61 (0.15) compared to 2.64 (0.09) l x min(-1)], and [La(-)](b) [6.7 (0.8) compared to 2.8 (0.4) mmol x l(-1)]. Moreover, mean HR during the Ironman triathlon cycle phase [146.3 (2.4) beats.min(-1); n=7] was significantly greater than mean HR during Bi(SSI) [130 (4) beats x min(-1)], and significantly less than mean HR during Bi(Th,vent) [159 (3) beats x min(-1); all P < 0.05]. However, HR during the cycle portion of the Ironman triathlon was highly related to (r = 0.873; P < 0.05) and not significantly different to HR(Th,vent) [150 (4) beats x min(-1)]. These data suggest that ultra-endurance triathletes cycle during the Ironman triathlon at a HR intensity that approximates to HR(Th,vent), but at a PO that is significantly below PO(Th,vent).

Adult↗

PubMed1982

A comparison of gas exchange indices used to detect the anaerobic threshold.

This study was undertaken to determine which of four commonly used ventilatory or gas exchange indices provides the most accurate and reliable detection of the anaerobic threshold (AT). Sixteen subjects performed two cycle ergometer tests to volitional fatigue. After 4 min of unloaded cycling, the work rate was increased 20 W/min. Ventilatory and gas exchange measurements were made every 30 s throughout each test. During one of the two tests (randomly assigned), venous blood was also sampled every 30 s for subsequent determinations of blood lactate (HLa) concentration. Four ventilatory and gas exchange indices (VE, VCO2, R, VE/VO2) were used separately to detect the AT. The AT determined from systematic increases in HLa concentration was used as the criterion measure. AT values (means +/- SE) (VO2, l/min) using VE, VCO2, R, VE/VO2, and HLa were 1.79 +/- 0.11, 1.74 +/- 0.11, 1.58 +/- 0.06, 1.84 +/- 0.11, and 1.85 +/- 0.11 l/min, respectively. The highest correlation between a ventilatory or gas exchange AT and ATHLa (i.e., criterion measure) was found for VE/VO2 (r=0.93, P less than 0.001). The VE/VO2 also provided the highest test-retest correlation for detection of the AT (r = 0.93, P less than 0.001). Multiple correlational analyses did not significantly enhance detection of the AT. These results favor the use of VE/VO2 for noninvasive detection of the AT because it proved to be the most sensitive and reliable ventilatory or gas exchange index studied.

Adult↗

PubMed1989

Detecting abnormalities in left ventricular function during exercise by respiratory measurement.

The degree of exercise-induced cardiac dysfunction and its relation to the anaerobic threshold were evaluated in 23 patients with chronic heart disease. A symptom-limited exercise test was performed with a cycle ergometer with work rate increased by 1 W every 6 seconds. Left ventricular function, as reflected by ejection fraction, was continuously monitored with a computerized cadmium telluride detector after the intravenous injection of technetium-labeled red blood cells. The anaerobic threshold (mean, 727 +/- 166 ml/min) was determined by the noninvasive measurement of respiratory gas exchange. As work rate rose, the left ventricular ejection fraction increased but reached a peak value at the anaerobic threshold and then fell below resting levels. Ejection fraction at rest, anaerobic threshold, and peak exercise were 41.4 +/- 11.3%, 46.5 +/- 12.0%, and 37.2 +/- 11.0%, respectively. Stroke volume also increased from rest (54.6 +/- 17.0 ml/beat) to the point of the anaerobic threshold (65.0 +/- 21.2 ml/beat) and then decreased at peak exercise (52.4 +/- 18.7 ml/beat). The slope of the plot of cardiac output versus work rate decreased above the anaerobic threshold. The anaerobic threshold occurred at the work rate above which left ventricular function decreased during exercise. Accurate determination of the anaerobic threshold provides an objective, noninvasive measure of the oxygen uptake above which exercise-induced deterioration in left ventricular function occurs in patients with chronic heart disease.

Anaerobic Threshold↗

PubMed1997

Children's and adolescents' anaerobic performance during cycle ergometry.

Cycle ergometry studies originated in the early 1900s but it was not until the early 1970s that the first studies of children and anaerobic performance were established. Since that time, research into the anaerobic performance of children and adolescents has proliferated, mainly due to attempts by investigators to overcome methodological problems. Besides the increase in studies using the most popular anaerobic test, the friction-braked Wingate, other tests such as the force-velocity and isokinetic cycle ergometers are becoming more common. No matter how the data are standardised, there is unequivocal agreement that children's and adolescents' anaerobic power scores are lower than those of adults. Qualitative muscular differences are often cited for this disparity rather than differences in the quantity of muscle, but conclusive research is lacking in this area. Despite the ethical considerations involved in studies with children, cycle ergometry has aided researchers to assess external short term power output, mean power and fatigue.

Adolescent↗

PubMed1999

Determination of the maximum steady state of lactate (MLSS) in saliva: an alternative to blood lactate determination.

Based on previous research which shows parallelism between the saliva and blood lactate response during incremental exercise, we hypothesized that a "maximum salivary lactate steady state" (saliva-MLSS) might exist. Thus, the aim of the present investigation was to establish 1) which lower limit for the increase in salivary lactate concentration during a constant workload (i.e., from the 10th to the 20th min) test could be used to determine the saliva-MLSS and 2) if the exercise intensity corresponding to the saliva-MLSS is identical to that evoking the (blood) MLSS. Twelve male amateur athletes of mean ( +/- SD) age 24 +/- 5 year were selected for the study. Based on the results of a previous maximal cycle ergometer test for lactate threshold (LT) determination, each subject performed consecutive constant workload tests of 20-min duration on separate days for MLSS determination. Blood and saliva (25 microl) samples were collected at 0, 10, and 20 min during the tests for lactate determination. A Student's t-test for paired data demonstrated that a salivary lactate increase of 0.8 mM corresponded to the saliva-MLSS. At this value, indeed, no significant differences were observed between the mean V(.)O(2) and W values corresponding to the MLSS and the saliva-MLSS. In conclusion, the present findings indicate that 0.8 mM is the lower limit for the increase in saliva lactate concentration during a constant load test and thus is that which might be used as a reference to determine saliva-MLSS. Furthermore, saliva-MLSS might be used as an alternative to MLSS determination in blood samples.

Adult↗

PubMed2006

Effect of different pedal rates on oxygen uptake slow component during constant-load cycling exercise.

AIM: We hypothesized that an extremely high pedal rate would induce much more type II muscle fibers recruitment even at an early phase of the same absolute work rate compared with normal pedal rates, and would result in changed amplitude of the pulmonary oxygen uptake slow component (VO(2)SC) during heavy constant-load exercise. METHODS: Two square-wave transitions of constant-load exercise were carried out at an exercise intensity corresponding to a VO(2) of 130% of the ventilatory threshold. The amplitude of the VO(2)SC in phase III during heavy constant-load exercise was determined at normal (60 rpm) and extremely high pedal rates (110 rpm). The VO(2) kinetics were analyzed by nonlinear regression. RESULTS: Although the absolute work rates were almost identical in the two pedal rates cycling exercise, the amplitude of the VO(2) in phase II (phase II amplitude), end-exercise VO(2) (EEVO(2)) and blood lactate accumulation ([La]) were significantly greater at 110 rpm than at 60 rpm (2 260+/-242 vs 1.830+/-304 mL.min(-1) for phase II amplitude; P<0.01, 2 350+/-265 vs 1 709+/-342 mL.min(-1) for EEVO(2); P<0.01, 6.4+/-1.3 vs 3.2+/-1.3 mmol.L(-1) for [La]; P<0.01, respectively). The amplitude of the VO(2)SC in phase III also revealed a significantly higher value at 110 rpm compared with 60 rpm (416+/-73 vs 201+/-89 mL.min(-1), P<0.01). In spite of the appearance of greater VO(2)SC at 110 rpm, no corresponding changes in integrals of the electromyography (EMG) signal and mean power frequency were observed. CONCLUSIONS: The results of this study indicate that the amplitude of the VO(2)SC was greater in higher pedal rate during the same work rate constant-load cycling exercise, which might be associated with a progressive increase in the adenosine triphosphate requirement of already recruited muscle fibers in exercising muscle.

Adult↗

PubMed2005

Aerodynamics of the human larynx during vocal fold vibration.

OBJECTIVES: : The goal of this study was to comprehensively analyze the influence of aerodynamics on laryngeal function. Three specific aspects were considered: 1) a multidimensional comparison of the interaction of subglottic pressure, sound intensity, and fundamental frequency; 2) examination of instantaneous changes in subglottic pressure during each glottic cycle; and 3) determination of the threshold subglottic pressure for vocal fold vibration and its dependence on other aerodynamic factors. STUDY DESIGN: : Prospective study with six healthy individuals without history of voice disorders. METHODS: : The subjects vocalized the vowel sound /i/ with a variety of different intensities, pitch, and sound intensity. Subglottic air pressure, fundamental frequency, sound intensity, and the electroglottography signal were simultaneously measured. RESULTS: : Linear relationships were seen in all subjects between subglottic air pressure and sound intensity, although there were large variations in the slopes of these relationships. Rapid variations in subglottic pressure during each glottic cycle were detected, corresponding to the opening of the vocal folds with each individual vibration. Threshold pressures for vocal fold vibration were dependent primarily on sound intensity and fundamental frequency and tended to be higher at vibration onset than at offset. CONCLUSION: : The larynx responded in a predictable pattern to general aerodynamic forces, but there was tremendous variability in its specific behavior. Fundamental frequency and sound intensity tended to increase with subglottic air pressure, but that relationship was not seen consistently in all subjects. The relationship between subglottic air pressure and sound intensity was usually linear, unlike the exponential relationship seen in previous studies. Subglottic pressure was noted to undergo rapid change with each glottic cycle in some, but not all, subjects and was most strongly affected by average subglottic pressure. Phonation threshold air pressure was influenced by the sound intensity and, to a smaller extent, by the fundamental frequency of the voiced sound.

Adult↗

PubMed2002

Measurement of ventilatory threshold by respiratory frequency.

This study was conducted to assess whether respiratory frequency can be used as a valid parameter for estimating ventilatory threshold and for examining differences in exercise modes such as a cycle ergometer and a treadmill. 24 men and 12 women performed an incremental exercise test to exhaustion on a cycle ergometer and on a treadmill. Oxygen uptake, carbon dioxide output, pulmonary ventilation, ventilatory frequency, and heart rate were measured continuously every 30 sec. during the test. Three different and independent reviewers detected the ventilatory threshold point and break point of respiratory rate, which were then compared. Analysis indicated that (1) ventilatory threshold was well correlated with break point of respiratory rate for both cycle (r=.88, p<.001) and treadmill exercise (r=.96, p<.001). However, on the average, ventilatory threshold was only 71% (cycle) or 88% (treadmill) of break point of respiratory rate. (2) The regression equation for treadmill exercise was more accurate than that for cycling, but the detected data samples were smaller. The break point of respiratory rate was more easily detected for the cycle ergometer test 33 of 36 subjects) than for the treadmill test (only 15 of 36). The cycle ergometer test identified the break point of respiratory rate more easily than did the treadmill test. (3) There was an association between physical fitness and whether the break point of respiratory rate was detectable, and the more fit the subject (above average), the more likely the break point was to be undetected. Our study demonstrates that the break point of respiratory rate is closely associated with ventilatory threshold and that the cycle ergometer test is more conducive than the treadmill test to the detectability of break point of respiratory rate.

Adolescent↗

PubMed2004

Effect of work rate on the functional 'gain' of Phase II pulmonary O2 uptake response to exercise.

It has recently been reported that the 'gain' of Phase II increase in pulmonary oxygen uptake (i.e. the 'fundamental' increase in V(O(2)) per unit increase in work rate; G(p)) does not attain the anticipated value of approximately 10 ml min(-1)W(-1) following the onset of high-intensity exercise. In the present study, we hypothesised that G(p) would fall significantly below 10 ml min(-1)W(-1) only when the work rate exceeded the so-called 'critical power' (CP). Seven healthy males completed several 'square-wave' transitions from 'unloaded' cycling to work rates requiring 60 and 90% of the gas exchange threshold (GET), 40 and 80% of the difference between the GET and V(O(2)) peak (i.e. below and above the CP, respectively), and 100, 110 and 120% of V(O(2)) peak. Pulmonary V(O(2)) was measured breath-by-breath and V(O(2)) kinetics were determined using non-linear regression techniques. The asymptotic G(p) was significantly lower at work rates above (7.2-8.6 ml min(-1)W(-1)) compared to work rates below (9.3-9.7 ml min(-1)W(-1)) the CP (P < 0.05). We conclude that the gain of Phase II increase in V(O(2)) becomes significantly reduced when the work rate exceeds the CP.

Adult↗

PubMed2003

Origin of electrical activation within the right atrial and left ventricular walls: differentiation by electrogram characteristics using the noncontact mapping system.

Clinical data using the noncontact mapping system (Ensite 3000) suggest that characteristics of the reconstructed unipolar electrograms may predict the origin of electrical activation within the atrial and ventricular walls (endocardial vs myocardial vs epicardial origin). Experimental data are lacking. In ten open-chest pigs (mean body weight 62 kg) cardiac pacing was performed at a cycle length of 600 ms with a pulse width of 2 ms and twice diastolic threshold from the endo-, the myo-, and the epicardium, respectively. Pacing was undertaken at three right atrial and three left ventricular sites, and cardiac activation was recorded with the Ensite system. Reconstructed unipolar electrograms at the location of earliest endocardial activation assessed by color coded isopotential maps were analyzed systematically for differences in morphology. The positive predictive value of atrial electrograms exhibiting an initial R wave during pacing for a subendocardial origin (i.e., myocardial or epicardial) was 0.96. The negative predictive value was 0.48. Electrograms generated during myocardial pacing exhibited increased maximal negative voltage and maximal dV/dt (-3 +/- 1.8 mV, -798 +/- 860 mV/ms, respectively) than the electrograms obtained during endocardial (-2 +/- 1 mV, -377 +/- 251 mV/ms, respectively) and epicardial pacing (-2.1 +/- 0.7 mV, -440 +/- 401 mV/ms, respectively, P<0.01 for both parameters). During pacing at the left ventricular wall, occurrence of an initial R wave did not differ significantly between electrograms reconstructed during endocardial and subendocardial pacing. All other characteristics of the unipolar ventricular electrograms analyzed, except latency, did not differ significantly when compared to stimulation depth. Morphological characteristics of unipolar electrograms generated by the noncontact mapping system during pacing of the atrium allowed for discrimination of an endocardial versus a subendocardial origin of activation. At the ventricular level, characteristics of unipolar electrograms did not predict the origin of cardiac activation in this experimental setting.

Analysis of Variance↗

PubMed2000

Exercise-induced lactate increase in relation to muscle substrates in patients with chronic obstructive pulmonary disease.

Early lactic acidosis has been suggested as negatively influencing the exercise capacity of patients with chronic obstructive pulmonary disease (COPD). We conducted a study to investigate whether the early lactate (La) response to exercise in COPD is related to alterations in exercise-related substrate levels in resting muscle, associated with physical inactivity. Twenty-seven COPD patients and 22 controls (physically inactive [PI] subjects, n = 15; and physically active [PA] subjects, n = 7) performed an incremental cycle test. Venous blood was sampled for La analyses, and the oxygen uptake at which the La level began to rise (La threshold) was calculated. Vastus lateralis biopsy specimens were obtained at rest. In the PA group, muscle glutamate (GLU) and glycogen were higher, but muscle La, pyruvate, and glucose were not different than in the PI group. Moreover, the La threshold was higher in the PA group. The COPD group had lower values for La threshold and muscle GLU, and higher values for muscle La and pyruvate levels than did the PI group. Stratification of patients into those with and without macroscopic emphysema (EMPH+, EMPH-, respectively), with comparable physical activity levels on the basis of previous observations, revealed lower values for La threshold and GLU in EMPH+ patients. Diffusing capacity for carbon monoxide (DL(CO)) and arterial oxygen tension (Pa(O(2))) in the four study groups were positively related to GLU and La threshold. Moreover, La threshold was positively related to GLU. This study illustrates that the early lactic acidosis during exercise in patients with COPD is associated with the physical inactivity-related reduction in these patient's muscle GLU. However, factors other than physical inactivity, such as Pa(O(2)) or DL(CO), play a role in the different La responses during exercise in subjects with different subtypes of COPD.

Aged↗

PubMed1993

Antisecretory effect of three premeal doses of cimetidine 400 mg versus a single morning dose of omeprazole 20 mg: pathophysiological implications for duodenal ulcer treatment.

The success of omeprazole in the healing of duodenal ulcer has been attributed to its profound and almost around-the-clock inhibition of acid, but the relevance of reducing meal-stimulated acid secretion exclusively has recently been emphasized in several clinical trials. For this reason, we used 24-h continuous intragastric pH monitoring to compare the pharmacodynamic effects of placebo, three fractioned premeal doses of cimetidine 400 mg and omeprazole 20 mg mane. Fifteen patients with duodenal ulcer in clinical remission were randomized to receive the above medications in single-blind fashion on three separate occasions, at least 2 wk apart. Both active regimens produced higher pH values (p < 0.05-0.001) than placebo, but omeprazole was much more effective than cimetidine (p < 0.01-0.001) during the various time intervals analyzed (24 h, evening, nighttime, daytime). The greater effectiveness of omeprazole was confirmed by its longer-lasting antisecretory action, insofar as the drug increased gastric pH above 3.0 units for about 21 h, whereas the daytime cimetidine regimen maintained this threshold for 7.30 h (p < 0.001) over the circadian cycle. As these markedly different pharmacodynamic effects have been proven to produce similar fast rates of duodenal ulcer healing in clinical trials, it is reasonable to assume that a small but well addressed reduction of gastric acidity can ensure the same therapeutic benefit as a strong and continuous acid inhibition. In this light, the acid peaks in response to meals seem to be important pathophysiological events, whose control is sufficient to permit quick ulcer healing.

Adult↗

PubMed2002

Recurrent inhibitory dynamics: the role of state-dependent distributions of conduction delay times.

We have formulated and analysed a dynamic model for recurrent inhibition that takes into account the state dependence of the delayed feedback signal (due to the variation in threshold of fibres with their size) and the distribution of these delays (due to the distribution of fibre diameters in the feedback pathway). Using a combination of analytic and numerical tools, we have analysed the behaviour of this model. Depending on the parameter values chosen, as well as the initial preparation of the system, there may be a spectrum of post-synaptic firing dynamics ranging from stable constant values through periodic bursting (limit cycle) behaviour and chaotic firing as well as bistable behaviours. Using detailed parameter estimation for a physiologically motivated example (the CA3-basket cell-mossy fibre system in the hippocampus), we present some of these numerical behaviours. The numerical results corroborate the results of the analytic characterization of the solutions. Namely, for some parameter values the model has a single stable steady state while for the others there is a bistability in which the eventual behaviour depends on the magnitude of stimulation (the initial function).

Animals↗

PubMed2000

Two-coil versus single-coil transvenous cardioverter defibrillator systems: comparative data.

Two types of new-generation transvenous implantable cardioverter defibrillator (ICD) systems, incorporating a two-coil (62 patients, group 1) versus single-coil (32 patients, group 2) lead system were compared among 94 consecutive patients. The two groups were comparable in age (58 +/- 13 vs 59 +/- 14 years), presenting arrhythmia (ventricular tachycardia versus ventricular fibrillation 77%/21% vs 84%/13%), cycle length of induced VT (294 +/- 4 vs 289 +/- 44 ms), number of unsuccessful antiarrhythmic drugs (1.7 +/- 0.8 vs 1.7 +/- 0.7), and left ventricular ejection fraction (35 +/- 12% vs 34 +/- 9%). Both systems were successfully implanted strictly transvenously in all patients. Biphasic shocks were used in all patients. Active shell devices were used in 79% and 84% patients of groups I and II, respectively (P = NS). Intraoperative testing revealed comparable defibrillation threshold (DFT) values (10.2 +/- 3.7 J in group 1 versus 9.3 +/- 3.6 J in group 2 system), and pacing threshold (0.7 +/- 0.3 vs 0.7 +/- 0.3 V), but R wave amplitude and lead impedance were lower in group 1 (13 +/- 5 vs 16 +/- 5 mV, P = 0.003; and 579 +/- 115 vs 657 +/- 111 ohms, P = 0.002, respectively). Lead insulation break requiring reoperation occurred in one patient with an Endotak lead, and two patients with Transvene leads had initially high DFT with a single one-lead/active can system, which was converted to a two- or three-endocardial-lead/inactive can configuration. We conclude that both single-coil and two-coil transvenous ICD systems were associated with high rates of successful strictly transvenous ICD implantation and a low incidence of lead-related complications. Significant differences were noted in the sensed R wave and lead impedance, probably reflecting the active fixation characteristics of the Transvene lead. However, in order to obviate the sporadic need for implantation of additional endocardial leads, as was the case in two patients in this series, a double-coil lead may be preferable.

Defibrillators, Implantable↗

PubMed2003

Oligonucleotide microarray for the study of functional gene diversity in the nitrogen cycle in the environment.

The analysis of functional diversity and its dynamics in the environment is essential for understanding the microbial ecology and biogeochemistry of aquatic systems. Here we describe the development and optimization of a DNA microarray method for the detection and quantification of functional genes in the environment and report on their preliminary application to the study of the denitrification gene nirS in the Choptank River-Chesapeake Bay system. Intergenic and intragenic resolution constraints were determined by an oligonucleotide (70-mer) microarray approach. Complete signal separation was achieved when comparing unrelated genes within the nitrogen cycle (amoA, nifH, nirK, and nirS) and detecting different variants of the same gene, nirK, corresponding to organisms with two different physiological modes, ammonia oxidizers and denitrifying halobenzoate degraders. The limits of intragenic resolution were investigated with a microarray containing 64 nirS sequences comprising 14 cultured organisms and 50 clones obtained from the Choptank River in Maryland. The nirS oligonucleotides covered a range of sequence identities from approximately 40 to 100%. The threshold values for specificity were determined to be 87% sequence identity and a target-to-probe perfect match-to-mismatch binding free-energy ratio of 0.56. The lower detection limit was 10 pg of DNA (equivalent to approximately 10(7) copies) per target per microarray. Hybridization patterns on the microarray differed between sediment samples from two stations in the Choptank River, implying important differences in the composition of the denitirifer community along an environmental gradient of salinity, inorganic nitrogen, and dissolved organic carbon. This work establishes a useful set of design constraints (independent of the target gene) for the implementation of functional gene microarrays for environmental applications.

Bacteria↗

PubMedDate not supplied

[Evaluation of the secretory activity of the adrenal cortex and gonads in women with epilepsy. II. Urinary excretion of estrogen fractions and alpha and beta pregnanediol during the 2 days preceding menstrual bleeding].

In 32 women with epileptic seizures related in time to the premenstrual phase (group A) and 31 women with seizures unrelated to this phase (group B) oestrone oestradiol and oestriol and progesterone metabolites (alpha and beta-pregnanediol) were determined in 24-hour urine. The investigations were carried out during 2 days preceding the onset of menstrual bleeding usually during three successive cycles. A significant reduction was observed in the amounts of all three oestrogen fractions in relation to normal values on both days (without any significant difference between the groups). Women with epilepsy excreted 56-60% less oestrogens than healthy women. Similarly the levels of alpha and beta-pregnanediol were significantly below the accepted normal range. The obtained results are insufficient for accepting the role of oestrogens in the development of lowered convulsive threshold on the days preceding menstrual bleeding. On the other hand, it may be concluded that progesterone deficiency may have an effect on the appearance of greater readiness to seizures before menstruation in epileptic women.

Adult↗

PubMed1996

Improvement in exercise tolerance and spirometric values in stable chronic obstructive pulmonary disease patients after an individualized outpatient rehabilitation programme.

OBJECTIVE: We sought to determine whether patients with stable chronic obstructive pulmonary disease (COPD) whose exercise performance is mainly limited by dyspnoea are able to improve their exercise tolerance after rehabilitation with an individualized programme based on aerobic training at the ventilatory threshold (VT) level. PATIENTS AND EXPERIMENTAL DESIGN: Thirteen stable and moderate to severe COPD patients took part in an outpatient rehabilitation programme lasting 4 months. This individualized programme consisted of exercise training (general training on cycle and upper-limb training by rowing at the heart rate corresponding to VT) together with provision of adequate calorie and protein support. RESULTS: Lung function test after rehabilitation revealed significant increases in FVC (82.9 vs 69.2 % pred) and FEV1 (47.2 vs 39.7 % pred), although FEV1/FVC were unchanged (44.8 vs 46.8%). Incremental exercise test performed on cycle revealed significant increases in time, work rate (82.0 vs 63.2 W), peak VO2 (14.6 vs 10.7 ml.kg-1.min-1), peak VO2 (840 vs 701 ml.min-1), peak VT (1309 vs 980 ml), and O2-pulse (8.3 vs 6.7). However, exercise tests were always symptom-limited by dyspnoea. CONCLUSIONS: We conclude that this individualized outpatient rehabilitation programme is able to improve exercise tolerance in stab le COPD patients affected by dyspnoea during exercise, through an apparent reconditioning of both skeletal and respiratory muscles and improved gas exchange during exercise, thus reducing the ratio of dead space to tidal volume. In consequence, patients whose exercise capacity is so reduced that they cannot develop significant lactic acidosis may reduce the ventilatory cost for exercise through this individualized therapy.

Aged↗